Systems and methods for material breakthrough

ABSTRACT

Methods may be performed to limit footing, pitch walking, and other alignment issues. The methods may include forming a treatment gas plasma within a processing region of a semiconductor processing chamber. The methods may further include directing effluents of the treatment gas plasma towards a semiconductor substrate within the processing region of the semiconductor processing chamber, and anisotropically modifying a surface of a first material on the semiconductor substrate with the effluents of the treatment gas plasma. The methods may also include passivating a surface of a second material on the semiconductor substrate with the effluents of the treatment gas plasma. The methods may further include forming a remote fluorine-containing plasma to produce fluorine-containing plasma effluents, and flowing the fluorine-containing plasma effluents to the processing region of the semiconductor processing chamber. The methods may also include selectively removing the modified surface of the first material from the semiconductor substrate.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/949,341, filed Apr. 10, 2018, which is hereby incorporated byreference in its entirety for all purposes.

TECHNICAL FIELD

The present technology relates to semiconductor systems, processes, andequipment. More specifically, the present technology relates to systemsand methods for selective etching.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers, or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess that etches one material faster than another facilitating, forexample, a pattern transfer process. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits, and processes, etch processes have been developedwith a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used inthe process. A wet HF etch preferentially removes silicon oxide overother dielectrics and materials. However, wet processes may havedifficulty penetrating some constrained trenches and also may sometimesdeform the remaining material. Dry etches produced in local plasmasformed within the substrate processing region can penetrate moreconstrained trenches and exhibit less deformation of delicate remainingstructures. However, local plasmas may damage the substrate and featuresformed on the substrate during subsequent process operations.Conventionally, feature damage, such as missing fin damage, is justaccepted as part of the process.

Thus, there is a need for improved systems and methods that can be usedto produce high quality devices and structures. These and other needsare addressed by the present technology.

SUMMARY

Exemplary etching methods may include forming a treatment gas plasmafrom a treatment gas precursor within a processing region of asemiconductor processing chamber. The etching methods may also includedirecting effluents of the treatment gas plasma towards a semiconductorsubstrate within the processing region of the semiconductor processingchamber. The etching methods may further include anisotropicallymodifying a surface of a first material on the semiconductor substratewith the effluents of the treatment gas plasma. The etching methods mayalso include passivating a surface of a second material on thesemiconductor substrate with the effluents of the treatment gas plasma.The etching methods may also include forming a remote plasma from afluorine-containing precursor to produce fluorine-containing plasmaeffluents. The etching methods may further include flowing thefluorine-containing plasma effluents to the processing region of thesemiconductor processing chamber. The etching methods may also includeselectively removing the modified surface of the first material from thesemiconductor substrate.

In some embodiments, the treatment gas precursor may include a mixtureof a first precursor and a second precursor. In some embodiments,anisotropically modifying the surface of the first material may includeanisotropically modifying the surface of the first material with plasmaeffluents of the first precursor. In some embodiments, the firstprecursor may include at least one of a nitrogen-containing precursor ora hydrogen-containing precursor. In some embodiments, passivating thesurface of the second material may include passivating the surface ofthe second material with plasma effluents of the second precursor. Insome embodiments, the second precursor may include at least one of anoxygen-containing precursor or a nitrogen-containing precursor. In someembodiments, the mixture may include less than or about 20% of thesecond precursor. In some embodiments, the first material may include aspacer material including an oxide material. In some embodiments, thesecond material may include a hardmask material including a nitridematerial.

The present technology may also include additional exemplary etchingmethods. The etching methods may include forming a treatment gas plasmawithin a processing region of a semiconductor processing chamber. Theetching methods may also include modifying a surface of a first materialon a semiconductor substrate within the processing region of thesemiconductor processing chamber with effluents of the treatment gasplasma. The etching methods may further include modifying a surface of asecond material on the semiconductor substrate with the effluents of thetreatment gas plasma. The etching methods may also include forming aremote plasma from a fluorine-containing precursor to producefluorine-containing plasma effluents. The etching methods may furtherinclude flowing the fluorine-containing plasma effluents to theprocessing region of the semiconductor processing chamber. The etchingmethods may also include flowing water vapor to the processing region ofthe semiconductor processing chamber. The etching methods may furtherinclude selectively removing the modified surface of the first materialfrom the semiconductor substrate.

In some embodiments, a temperature of the semiconductor substrate may bemaintained between about 5° C. and about 35° C. In some embodiments, thefluorine-containing plasma effluents may be formed in a remote region ofthe semiconductor processing chamber fluidly coupled with, andphysically separated from, the processing region of the semiconductorprocessing chamber. In some embodiments, the fluorine-containing plasmaeffluents may be produced by a capacitively-coupled plasma at a powerlevel of less than or about 300 W. In some embodiments, the firstmaterial may include a spacer material including an oxide material. Insome embodiments, the second material may include a hardmask materialincluding a nitride material. In some embodiments, the etching methodsmay include a selectivity of at least 7:1 of the modified first materialrelative to the modified second material.

The present technology may further include additional exemplary etchingmethods. The etching methods may include forming a bias plasma from acarbon-containing precursor within a processing region of asemiconductor processing chamber to produce carbon-containing plasmaeffluents. The etching methods may also include selectively depositing acarbon-containing protective layer at a surface of a first material on asemiconductor substrate within the processing region of thesemiconductor processing chamber with the carbon-containing plasmaeffluents. The etching methods may further include selectively removinga surface of a second material on the semiconductor substrate.

In some embodiments, the carbon-containing precursor may includemethane. In some embodiments, the carbon-containing precursor furthermay include a dilution gas. In some embodiments, a ratio of a flow rateof the dilution gas to a flow rate of methane may be about 2:1. In someembodiments, the etching methods may also include depositing acarbon-containing protective layer at a surface of the second material.In some embodiments, a ratio of a thickness of the carbon-containingprotective layer deposited at the surface of the first material to athickness of the carbon-containing protective layer deposited at thesurface of the second material may be at least about 3:1.

In some embodiments, the etching methods may also include forming atreatment gas plasma from a treatment gas precursor within theprocessing region of the semiconductor processing chamber. The etchingmethods may further include anisotropically modifying the surface of thesecond material with effluents of the treatment gas plasma. The etchingmethods may also include forming a remote plasma from afluorine-containing precursor to produce fluorine-containing plasmaeffluents. The etching methods may further include flowing thefluorine-containing plasma effluents to the processing region of thesemiconductor processing chamber. The etching methods may also includeselectively removing the modified surface of the first material from thesemiconductor substrate with the fluorine-containing plasma effluents.

In some embodiments, the carbon-containing precursor may include afluorine and carbon-containing precursor. In some embodiments, thecarbon-containing precursor further may include a dilution gas. In someembodiments, a ratio of a flow rate of the dilution gas to a flow rateof the fluorine and carbon-containing precursor may be between about20:1 and about 200:1.

Such technology may provide numerous benefits over conventional systemsand techniques. For example, the technology may selectively removespacer materials relative to hardmask materials, and footing issues maybe prevented or limited. Additionally, given the directional oranisotropic etching provided by the technology, critical dimensions ofspacers may be maintained and pitch walking and other alignment issuesmay be avoided. These and other embodiments, along with many of theiradvantages and features, are described in more detail in conjunctionwith the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedtechnology may be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 shows a top plan view of an exemplary processing system accordingto the present technology.

FIG. 2 shows a schematic cross-sectional view of an exemplary processingchamber according to the present technology.

FIG. 3 shows selected operations in an etching method according toembodiments of the present technology.

FIGS. 4A-4G illustrate cross-sectional views of substrate materials onwhich selected operations are being performed according to embodimentsof the present technology.

FIG. 5 shows selected operations in an etching method according toembodiments of the present technology.

FIGS. 6A and 6B illustrate cross-sectional views of substrate materialson which selected operations are being performed according toembodiments of the present technology.

FIGS. 7A-7C illustrate cross-sectional views of substrate materials onwhich selected operations are being performed according to embodimentsof the present technology.

FIG. 8 shows selected operations in an etching method according toembodiments of the present technology.

FIGS. 9A-9C illustrate cross-sectional views of substrate materials onwhich selected operations are being performed according to embodimentsof the present technology.

Several of the figures are included as schematics. It is to beunderstood that the figures are for illustrative purposes, and are notto be considered of scale unless specifically stated to be of scale.Additionally, as schematics, the figures are provided to aidcomprehension and may not include all aspects or information compared torealistic representations, and may include superfluous or exaggeratedmaterial for illustrative purposes.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a letter thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the letter.

DETAILED DESCRIPTION

The present technology includes systems and components for semiconductorprocessing of small pitch features. Multi-patterning techniques, such asSelf-Aligned Double Patterning (SADP) or Self-Aligned QuadruplePatterning (SAQP), have been developed to enhance feature density forintegrated circuits. Such multi-patterning techniques often involveforming multiple masks or barrier layers, such as mandrels, spacers,hardmask or etch stop layers, etc., and subsequently selectivelyremoving or etching the masks or barrier layers at various processingsteps. As line pitch continues to decrease, the dimensions, e.g., widthor depths, of the masks or barrier layers employed are also reduced,which puts stringent requirements on mask losses, such as lateral spacerloss, loss of hardmask or etch stop layers. Conventional reactive ionetching processes have struggled to meet these requirements due to thesputtering component involved, which leads to faceted or more taperedspacer profiles at the top of the spacers, reduction or thinning of thespacer critical dimension, and loss of the hardmask or etch stop layers.Sputtering also creates footing along the spacer sidewalls. Mask lossesand footing further lead to pitch walking and transferability issues.These issues become more prominent especially for sub-10 or sub-7 nmtechnology nodes with very small spacer critical dimensions.

The present technology takes advantage of a single chamber capable ofboth surface modification as well as etching capabilities to affectmaterial quality, etch rates, and selectivity. Utilizing a bias plasma,directional or anisotropic modification of exposed areas may beachieved. The present technology also provides a variety of methods andetching chemistries that offers high etching selectivity of modifiedmaterials over unmodified materials. The present technology alsoprovides methods and etching chemistries that improve etchingselectivity of spacer materials over hardmask materials. As such, a flattop surface of etched spacers may be achieved, and spacer sidewallcritical dimension may be maintained. Hardmask layer loss may also beprevented or minimized. The present technology reduces footing andprevents pitch walking and other alignment issues.

Although the remaining disclosure will routinely identify specificetching processes utilizing the disclosed technology, it will be readilyunderstood that the systems and methods are equally applicable todeposition and cleaning processes as may occur in the describedchambers. Accordingly, the technology should not be considered to be solimited as for use with etching processes alone.

FIG. 1 shows a top plan view of one embodiment of a processing system100 of deposition, etching, baking, and curing chambers according toembodiments. The processing tool 100 depicted in FIG. 1 may contain aplurality of process chambers, 114A-D, a transfer chamber 110, a servicechamber 116, an integrated metrology chamber 117, and a pair of loadlock chambers 106A-B. The process chambers may include structures orcomponents similar to those described in relation to FIG. 2, as well asadditional processing chambers.

To transport substrates among the chambers, the transfer chamber 110 maycontain a robotic transport mechanism 113. The transport mechanism 113may have a pair of substrate transport blades 113A attached to thedistal ends of extendible arms 113B, respectively. The blades 113A maybe used for carrying individual substrates to and from the processchambers. In operation, one of the substrate transport blades such asblade 113A of the transport mechanism 113 may retrieve a substrate Wfrom one of the load lock chambers such as chambers 106A-B and carrysubstrate W to a first stage of processing, for example, an etchingprocess as described below in chambers 114A-D. If the chamber isoccupied, the robot may wait until the processing is complete and thenremove the processed substrate from the chamber with one blade 113A andmay insert a new substrate with a second blade (not shown). Once thesubstrate is processed, it may then be moved to a second stage ofprocessing. For each move, the transport mechanism 113 generally mayhave one blade carrying a substrate and one blade empty to execute asubstrate exchange. The transport mechanism 113 may wait at each chamberuntil an exchange can be accomplished.

Once processing is complete within the process chambers, the transportmechanism 113 may move the substrate W from the last process chamber andtransport the substrate W to a cassette within the load lock chambers106A-B. From the load lock chambers 106A-B, the substrate may move intoa factory interface 104. The factory interface 104 generally may operateto transfer substrates between pod loaders 105A-D in an atmosphericpressure clean environment and the load lock chambers 106A-B. The cleanenvironment in factory interface 104 may be generally provided throughair filtration processes, such as HEPA filtration, for example. Factoryinterface 104 may also include a substrate orienter/aligner (not shown)that may be used to properly align the substrates prior to processing.At least one substrate robot, such as robots 108A-B, may be positionedin factory interface 104 to transport substrates between variouspositions/locations within factory interface 104 and to other locationsin communication therewith. Robots 108A-B may be configured to travelalong a track system within enclosure 104 from a first end to a secondend of the factory interface 104.

The processing system 100 may further include an integrated metrologychamber 117 to provide control signals, which may provide adaptivecontrol over any of the processes being performed in the processingchambers. The integrated metrology chamber 117 may include any of avariety of metrological devices to measure various film properties, suchas thickness, roughness, composition, and the metrology devices mayfurther be capable of characterizing grating parameters such as criticaldimensions, sidewall angle, and feature height under vacuum in anautomated manner.

Turning now to FIG. 2 is shown a cross-sectional view of an exemplaryprocess chamber system 200 according to the present technology. Chamber200 may be used, for example, in one or more of the processing chambersections 114 of the system 100 previously discussed Generally, the etchchamber 200 may include a first capacitively-coupled plasma source toimplement an ion milling operation and a second capacitively-coupledplasma source to implement an etching operation and to implement anoptional deposition operation. The chamber 200 may include groundedchamber walls 240 surrounding a chuck 250. In embodiments, the chuck 250may be an electrostatic chuck that clamps the substrate 202 to a topsurface of the chuck 250 during processing, though other clampingmechanisms as would be known may also be utilized. The chuck 250 mayinclude an embedded heat exchanger coil 217. In the exemplaryembodiment, the heat exchanger coil 217 includes one or more heattransfer fluid channels through which heat transfer fluid, such as anethylene glycol/water mix, may be passed to control the temperature ofthe chuck 250 and ultimately the temperature of the substrate 202.

The chuck 250 may include a mesh 249 coupled to a high voltage DC supply248 so that the mesh 249 may carry a DC bias potential to implement theelectrostatic clamping of the substrate 202. The chuck 250 may becoupled with a first RF power source and in one such embodiment, themesh 249 may be coupled with the first RF power source so that both theDC voltage offset and the RF voltage potentials are coupled across athin dielectric layer on the top surface of the chuck 250. In theillustrative embodiment, the first RF power source may include a firstand second RF generator 252, 253. The RF generators 252, 253 may operateat any industrially utilized frequency, however in the exemplaryembodiment the RF generator 252 may operate at 60 MHz to provideadvantageous directionality. Where a second RF generator 253 is alsoprovided, the exemplary frequency may be 2 MHz.

With the chuck 250 to be RF powered, an RF return path may be providedby a first showerhead 225. The first showerhead 225 may be disposedabove the chuck to distribute a first feed gas into a first chamberregion 284 defined by the first showerhead 225 and the chamber wall 240.As such, the chuck 250 and the first showerhead 225 form a first RFcoupled electrode pair to capacitively energize a first plasma 270 of afirst feed gas within a first chamber region 284. A DC plasma bias, orRF bias, resulting from capacitive coupling of the RF powered chuck maygenerate an ion flux from the first plasma 270 to the substrate 202,e.g., He ions where the first feed gas is He, to provide an ion millingplasma. The first showerhead 225 may be grounded or alternately coupledwith an RF source 228 having one or more generators operable at afrequency other than that of the chuck 250, e.g., 13.56 MHz or 60 MHz.In the illustrated embodiment the first showerhead 225 may be selectablycoupled to ground or the RF source 228 through the relay 227 which maybe automatically controlled during the etch process, for example by acontroller (not shown). In disclosed embodiments, chamber 200 may notinclude showerhead 225 or dielectric spacer 220, and may instead includeonly baffle 215 and showerhead 210 described further below.

As further illustrated in the figure, the etch chamber 200 may include apump stack capable of high throughput at low process pressures. Inembodiments, at least one turbo molecular pump 265, 266 may be coupledwith the first chamber region 284 through one or more gate valves 260and disposed below the chuck 250, opposite the first showerhead 225. Theturbo molecular pumps 265, 266 may be any commercially available pumpshaving suitable throughput and more particularly may be sizedappropriately to maintain process pressures below or about 50 mTorr orbelow or about 20 mTorr at the desired flow rate of the first feed gas,e.g., 50 to 500 sccm of He where helium is the first feed gas. In theembodiment illustrated, the chuck 250 may form part of a pedestal whichis centered between the two turbo pumps 265 and 266, however inalternate configurations chuck 250 may be on a pedestal cantileveredfrom the chamber wall 240 with a single turbo molecular pump having acenter aligned with a center of the chuck 250.

Disposed above the first showerhead 225 may be a second showerhead 210.In one embodiment, during processing, the first feed gas source, forexample, helium delivered from gas distribution system 290 may becoupled with a gas inlet 276, and the first feed gas flowed through aplurality of apertures 280 extending through second showerhead 210, intothe second chamber region 281, and through a plurality of apertures 282extending through the first showerhead 225 into the first chamber region284. An additional flow distributor or baffle 215 having apertures 278may further distribute a first feed gas flow 216 across the diameter ofthe etch chamber 200 through a distribution region 218. In an alternateembodiment, the first feed gas may be flowed directly into the firstchamber region 284 via apertures 283 which are isolated from the secondchamber region 281 as denoted by dashed line 223.

Chamber 200 may additionally be reconfigured from the state illustratedto perform an etching operation. A secondary electrode 205 may bedisposed above the first showerhead 225 with a second chamber region 281there between. The secondary electrode 205 may further form a lid or topplate of the etch chamber 200. The secondary electrode 205 and the firstshowerhead 225 may be electrically isolated by a dielectric ring 220 andform a second RF coupled electrode pair to capacitively discharge asecond plasma 292 of a second feed gas within the second chamber region281. Advantageously, the second plasma 292 may not provide a significantRF bias potential on the chuck 250. At least one electrode of the secondRF coupled electrode pair may be coupled with an RF source forenergizing an etching plasma. The secondary electrode 205 may beelectrically coupled with the second showerhead 210. In an exemplaryembodiment, the first showerhead 225 may be coupled with a ground planeor floating and may be coupled to ground through a relay 227 allowingthe first showerhead 225 to also be powered by the RF power source 228during the ion milling mode of operation. Where the first showerhead 225is grounded, an RF power source 208, having one or more RF generatorsoperating at 13.56 MHz or 60 MHz, for example, may be coupled with thesecondary electrode 205 through a relay 207 which may allow thesecondary electrode 205 to also be grounded during other operationalmodes, such as during an ion milling operation, although the secondaryelectrode 205 may also be left floating if the first showerhead 225 ispowered.

A second feed gas source, such as nitrogen trifluoride, and a hydrogensource, such as ammonia, may be delivered from gas distribution system290, and coupled with the gas inlet 276 such as via dashed line 224. Inthis mode, the second feed gas may flow through the second showerhead210 and may be energized in the second chamber region 281. Reactivespecies may then pass into the first chamber region 284 to react withthe substrate 202. As further illustrated, for embodiments where thefirst showerhead 225 is a multi-channel showerhead, one or more feedgases may be provided to react with the reactive species generated bythe second plasma 292. In one such embodiment, a water source may becoupled with the plurality of apertures 283. Additional configurationsmay also be based on the general illustration provided, but with variouscomponents reconfigured. For example, flow distributor or baffle 215 maybe a plate similar to the second showerhead 210, and may be positionedbetween the secondary electrode 205 and the second showerhead 210. Asany of these plates may operate as an electrode in variousconfigurations for producing plasma, one or more annular or other shapedspacer may be positioned between one or more of these components,similar to dielectric ring 220. Second showerhead 210 may also operateas an ion suppression plate in embodiments, and may be configured toreduce, limit, or suppress the flow of ionic species through the secondshowerhead 210, while still allowing the flow of neutral and radicalspecies. One or more additional showerheads or distributors may beincluded in the chamber between first showerhead 225 and chuck 250. Sucha showerhead may take the shape or structure of any of the distributionplates or structures previously described. Also, in embodiments a remoteplasma unit (not shown) may be coupled with the gas inlet to provideplasma effluents to the chamber for use in various processes.

In an embodiment, the chuck 250 may be movable along the distance H2 ina direction normal to the first showerhead 225. The chuck 250 may be onan actuated mechanism surrounded by a bellows 255, or the like, to allowthe chuck 250 to move closer to or farther from the first showerhead 225as a means of controlling heat transfer between the chuck 250 and thefirst showerhead 225, which may be at an elevated temperature of 80°C.-150° C., or more. As such, an etch process may be implemented bymoving the chuck 250 between first and second predetermined positionsrelative to the first showerhead 225. Alternatively, the chuck 250 mayinclude a lifter 251 to elevate the substrate 202 off a top surface ofthe chuck 250 by distance H1 to control heating by the first showerhead225 during the etch process. In other embodiments, where the etchprocess is performed at a fixed temperature such as about 90-110° C. forexample, chuck displacement mechanisms may be avoided. A systemcontroller (not shown) may alternately energize the first and secondplasmas 270 and 292 during the etching process by alternately poweringthe first and second RF coupled electrode pairs automatically.

The chamber 200 may also be reconfigured to perform a depositionoperation. A plasma 292 may be generated in the second chamber region281 by an RF discharge which may be implemented in any of the mannersdescribed for the second plasma 292. Where the first showerhead 225 ispowered to generate the plasma 292 during a deposition, the firstshowerhead 225 may be isolated from a grounded chamber wall 240 by adielectric spacer 230 so as to be electrically floating relative to thechamber wall. In the exemplary embodiment, an oxidizer feed gas source,such as molecular oxygen, may be delivered from gas distribution system290, and coupled with the gas inlet 276. In embodiments where the firstshowerhead 225 is a multi-channel showerhead, any silicon-containingprecursor, such as OMCTS for example, may be delivered from gasdistribution system 290, and directed into the first chamber region 284to react with reactive species passing through the first showerhead 225from the plasma 292. Alternatively the silicon-containing precursor mayalso be flowed through the gas inlet 276 along with the oxidizer.Chamber 200 is included as a general chamber configuration that may beutilized for various operations discussed in reference to the presenttechnology. The chamber is not to be considered limiting to thetechnology, but instead to aid in understanding of the processesdescribed. Several other chambers known in the art or being developedmay be utilized with the present technology including any chamberproduced by Applied Materials Inc. of Santa Clara, Calif., or anychamber that may perform the techniques described in more detail below.

FIG. 3 illustrates exemplary operations of a method 300 that may beperformed, for example, in the chamber 200 as previously described.Prior to the first operation of the method, a substrate may be processedin one or more ways before being placed within a processing region of achamber in which method 300 may be performed. For example, films orlayers may be deposited, grown, or otherwise formed on the substrates,and masks for patterning the films or layers may be formed to producefeatures. FIG. 4A illustrates a portion of such a processed structure400, which may be produced during a multi-patterning process. Theprocessed structure 400 may be further developed in producing, forexample, fin-based structures, or any other semiconductor structures,using method 300, the operations of which will be described inconjunction with the schematic illustration of FIGS. 4A-4G.

With reference to FIG. 4A, the processed structure 400 may include ahardmask or etch stop layer 405, one or more patterned structures ormandrels 410, and a spacer material layer 415 overlaying the hardmasklayer 405 and the mandrels 410. Although two mandrels 410 are shown inFIG. 4A, the processed structure 400 may include more or fewer mandrels410. The mandrels 410 may include a semiconductor material, such assilicon. In some embodiments, the mandrels 410 may be or may includepolysilicon mandrels 410. The spacer material layer 415 may include anoxide, such as silicon oxide or other oxide that may be used or usefulin semiconductor processes. The hardmask layer 405 may include anitride, such as silicon nitride, titanium nitride, or other nitride orhardmask materials that may resist etching during the etching processfor the spacer material 415 and the mandrels 410 as discussed below.Although not shown, the processed structure 400 may include additionallayers below the hardmask layer 405 overlaying a substrate. In someembodiments, the processed structure 400 may be produced in the sameprocessing chamber as the processing chamber in which method 300 may beperformed, or may be produced in a different processing chamber and thentransferred to the processing chamber in which method 300 may beperformed.

Once the processed structure 400 may be positioned within a processingregion of a semiconductor processing chamber, such as the first chamberregion 284 of the processing chamber 200 discussed above with referenceto FIG. 2, method 300 may be initiated by forming a treatment gas plasmaformed from a treatment gas precursor within the processing region atoperation 305. Such a plasma is similarly understood to be a wafer-levelplasma. The plasma of the treatment gas precursor may be a bias plasma,providing directional flow of the plasma effluents 420 of the treatmentgas precursor towards the processed structure 400 at operation 310, asillustrated in FIG. 4B. At operation 315, the plasma effluents 420 ofthe treatment gas precursor may modify the exposed region of theprocessed structure 400, such as the spacer material layer 415. Giventhe directional flow of the plasma effluents 420, modification may beanisotropic. Modified layers 425 a may be formed at the top surfaceregions of the spacer material layer 415, and modified layers 425 b mayalso be formed at the bottom surface regions of the spacer materiallayer 415. Modification may not occur along sidewalls of the spacermaterial layer 415.

A remote plasma may be formed at operation 320 to produce plasmaeffluents, and the remote plasma may include or be composed of ahalogen-containing precursor. At operation 325, the plasma effluents maybe flowed through the processing chamber to the processing region of theprocessing chamber where the processed structure 400 may be housed. Inembodiments, the plasma utilized in operation 320 may also be formed atthe wafer level, but ions of a remote plasma may be filtered out by ashowerhead or other structure through which the effluents may be flowedat operation 325, thereby reducing a sputtering component at the wafer.Upon contacting the modified layers 425, at operation 330, the plasmaeffluents may remove the modified layers 425 of the spacer materiallayer 415. The plasma effluents may have an etching selectivity of themodified layers 425 to the unmodified portion of the spacer materiallayer 415. As such, at operation 330, the plasma effluents may removethe modified layers 425 but may have very limited, or substantially noremoval of the exposed, unmodified sidewalls of the spacer materiallayer 415 or the subsequently exposed, unmodified portion of the spacermaterial layer 415, resulting in the processed structure 400 as shown inFIG. 4C. Because only the depth dimension of the spacer material layer415 may be reduced through performance of method 300, the widthdimension of the sidewalls of the spacer material layer 415 may besubstantially maintained, and critical dimension uniformity of thespacers may be maintained.

The treatment gas precursors involved in operations 305-315 formodifying the spacer material layer 415 may include one or more inertgas materials, such as helium, neon, argon, etc. The treatment gasprecursors may also include precursors that may have limited chemicalactivity or may be unreactive with the spacer material layer 415, suchas oxygen-containing precursors and/or hydrogen-containing precursors.The oxygen-containing precursors may include diatomic oxygen, carbonoxide, such as carbon dioxide, nitrogen oxide, such as dinitrogenmonoxide, or other precursors including oxygen. The hydrogen-containingprecursors may include diatomic hydrogen, ammonia, or other precursorsincluding hydrogen.

The bias plasma involved in operations 305-315 for providing directionalflow of the plasma effluents 420 towards the surface of the spacermaterial layer 415 of the processed structure 400 may be a low-levelplasma to limit sputtering of the exposed regions of the processedstructure 400 and to control the amount or depth of surfacemodification. In some embodiments, the plasma power may be less than orabout 500 W, less than or about 450 W, less than or about 400 W, lessthan or about 350 W, less than or about 300 W, less than or about 250 W,less than or about 200 W, less than or about 150 W, less than or about100 W, less than or about 75 W, less than or about 50 W, less than orabout 25 W, less than or about 20 W, less than or about 15 W, less thanor about 10 W, less than or about 5 W, or less, depending on thetreatment gas precursor utilized and the desired depth of themodification. For example, when the plasma effluents 420 of thetreatment gas precursors may include relatively small or lightmaterials, such as hydrogen ions, a higher bias power, such as about 40W or more, may be utilized to achieve a desired depth of modification.To achieve a similar depth of modification, when the plasma effluents420 of the treatment gas precursors may include relatively large orheavy material, such as argon ions, a lower bias power, such as 30 W orless, may be utilized to direct the flow of argon ions.

Depending on the treatment gas precursors and the bias plasma poweremployed, the depth of the modified layers 425 as shown in FIG. 4B maybe about 1 nm, about 2 nm, about 3 nm, about 4 nm, or more, which inturn may lead to about 1 nm, about 2 nm, about 3 nm, about 4 nm, or morematerial removal at the removal operation 330. Depending on theparticular application, operations 305-330 may be repeated in cycles toremove the spacer material layer 415 until the mandrels 410 and/or thehardmask layer 405 underlying the spacer material layer 415 may beexposed. In some embodiments, operations 305-330 may be performed for 1cycle, 2 cycles, 3 cycles, 4 cycles, 5 cycles, or more in order toexpose the mandrel 410 and/or the hardmask layer 405 underneath thespacer material layer 415. In some embodiments, during each cycle, themodification operation 315 may last less than or about 80 seconds, lessthan or about 70 seconds, less than or about 60 seconds, less than orabout 50 seconds, less than or about 40 seconds, less than or about 30seconds, less than or about 20 seconds, less than or about 10 seconds,less than or about 5 seconds, or less in embodiments, depending on thedesired thickness of the spacer material layer 415 to be modified andthus removed in the subsequent removal operation 330.

The pressure within the processing chamber may be controlled during themodification operation 315 as well. For example, while forming the biasplasma and performing the modification operation 315, the pressurewithin the processing region may be maintained below or about 1 Torr. Insome embodiments, the pressure within the processing chamber may bemaintained below or about 700 mTorr, below or about 600 mTorr, below orabout 500 mTorr, below or about 400 mTorr, below or about 300 mTorr,below or about 250 mTorr, below or about 200 mTorr, below or about 150mTorr, below or about 100 mTorr, below or about 80 mTorr, below or about60 mTorr, below or about 40 mTorr, below or about 20 mTorr, below orabout 10 mTorr, below or about 5 mTorr, below or about 3 mTorr, orlower. Relatively lower pressures within the processing region may bedesired so as to increase the mean free path of the particles of plasmaeffluents 420 and to increase the directionality of the modificationoperation 315.

The plasma involved in operations 320-330 may be formed remotely fromthe processing region of the processing chamber. For example, the plasmamay be formed in a region of the processing chamber that is fluidlyisolated from the processing region of the processing chamber. Thus, theremote plasma region may be physically separated from the processingregion, while being fluidly coupled with the processing region. Forexample, in the exemplary chamber of FIG. 2, the remote plasma may begenerated in region 281, which is separated from the processing region284 by the showerhead 225. Additionally, the remote plasma may be formedin a remote plasma unit, such as an RPS unit that is separate from thechamber, but fluidly coupled with the chamber to deliver plasmaeffluents into the chamber, such as through a lid, top plate, orshowerhead.

The remote plasma power involved in operations 320-330 may be greaterthan the wafer-level bias plasma power involved in operations 305-315because ions or charged particulars may be removed from the plasmaeffluents by the showerhead as the plasma effluents travel towards theprocessing region where the processed structure 400 may be housed. Insome embodiments, the remote plasma power involved in operations 320-330may be between about 50 W and about 500 W. In some embodiments, theremote plasma power may be less than or about 450 W, less than or about400 W, less than or about 350 W, less than or about 300 W, less than orabout 250 W, less than or about 200 W, less than or about 150 W, lessthan or about 100 W, less than or about 75 W, less than or about 50 W,or less.

The remote plasma involved in operations 320-330 may be formed from oneor more precursors including a halogen-containing precursor, such asincluding a fluorine-containing precursor, for example. Thefluorine-containing precursor may include one or more materialsincluding NF₃, HF, F₂, CF₄, CHF₃, C₂F₆, C₃F₆, BrF₃, ClF₃, SF₆, oradditional fluorine-substituted hydrocarbons, or fluorine-containingmaterials. The fluorine-containing precursor may be flowed into theremote plasma region to generate plasma effluents, such asfluorine-containing plasma effluents.

A source of hydrogen may also be incorporated as an etchant precursor,and may include hydrogen, ammonia, or any other incompletely substitutedhydrocarbon, or other hydrogen-containing material. The source ofhydrogen, such as ammonia, for example, may be delivered with thefluorine-containing precursor into the remote plasma region duringplasma formation, and thus the plasma effluents may also includehydrogen-containing plasma effluents. The source of hydrogen may alsobypass the remote plasma region and be delivered into the processingregion where it may be radicalized through interaction with thefluorine-containing plasma effluents. In either scenario, the plasmaeffluents may be delivered to the processing region of the semiconductorprocessing chamber where they may contact or interact with the modifiedlayer 425 of the spacer material layer 415 of the processed structure400. Helium or other carrier gas may also be included for uniformdistribution of the plasma effluents when flowed through the showerheadinto the processing region.

As discussed above, only a thin surface layer of the spacer materiallayer 415 may be modified during the modification process, and the depthof the modified layers 425 may be between only a few nanometers or less,the amount of fluorine-containing precursor flowed during the removalprocess may be controlled at relatively low level. In some embodiments,the flow rate of the fluorine-containing precursor may be maintainedbelow or about 30 sccm, below or about 25 sccm, below or about 20 sccm,below or about 15 sccm, below or about 10 sccm, below or about 5 sccm,or lower. The flow rate of the hydrogen-containing precursor and/or thecarrier gases may be maintained above or about 10 sccm, above or about50 sccm, above or about 100 sccm, above or about 150 sccm, above orabout 200 sccm above or about 250 sccm, above or about 300 sccm, aboveor about 350 sccm, above or about 400 sccm, above or about 500 sccm,above or about 600 sccm, above or about 700 sccm, above or about 800sccm, above or about 900 sccm, above or about 1,000 sccm, or greater. Arelatively low ratio of the fluorine-containing precursor tohydrogen-containing precursor and/or carrier gases may facilitateremoving only the modified layers 425 and thus improve the selectivityof the modified layer 425 over the unmodified spacer material layer 415.In some embodiments, operations 305-330 of method 300 may achieve aselectivity of modified portions of the spacer material layer 415 tounmodified portions of the spacer material layer 415 greater than orabout 10:1, greater than or about 20:1, greater than or about 40:1,greater than or about 100:1, greater than or about 1,000:1, or up toabout 1:0 at which point the modified portion of the spacer materiallayer 415 may etch, but the unmodified portion of the spacer materiallayer 415 may not etch.

During the operations 320-330, a temperature of the processed structure400 or the processing region may be maintained above or about 50° C.,above or about 60° C., above or about 70° C., above or about 80° C.,above or about 90° C., above or about 100° C., above or about 110° C.,above or about 120° C., above or about 130° C., above or about 140° C.,or above or about 150° C., or higher. In some embodiments, thetemperature of the processed structure 400 or the processing region maybe maintained between about 80° C. and about 110° C. to selectively etchthe modified layers 425 while the unmodified portions of the spacermaterial layer 415 may not be etched with the removal process. Becausethe modification process involving operations 305-315 may be lesssensitive to the temperature of the processed structure 400 and/or theprocessing region of the chamber, temperature of the processed structure400 and/or the processing region may be maintained at a temperature thesame as or similar to that maintained during the removal processinvolving operations 320-330.

As discussed above, depending on particular applications, operations305-330 may be repeated in cycles to remove the spacer material layer415 until the mandrels 410 and/or the hardmask layer 405 underlying thespacer material layer 415 may be exposed. Although the spacer materiallayer 415 may be deposited as a blanket layer, the thickness of theportion of the spacer material layer 415 near a top region of themandrels 410 and the thickness of the portion of the spacer materiallayer 415 near a bottom region of the mandrels 410, such as the portionoverlaying the hardmask layer 405 between the mandrels 410, may vary.For example, the portion of the spacer material layer 415 near the topregion of the mandrels 410 may have a greater thickness than that of theportion of the spacer material layer 415 near the bottom region of themandrels 410 overlaying portions of the hardmask layer 405, or viceversa. As such, after performing operations 305-330 for multiple cycles,the hardmask layer 405, or portions thereof, may be exposed, whereas themandrels 410 may not be completely exposed, such as shown in FIG. 4D.Although FIG. 4D illustrates the scenario where the remaining spacermaterial layer 415 overlaying the top region of the mandrels 410 mayinclude a greater thickness than the remaining spacer material layer 415that may overlay portions of hardmask layer 405, in some embodiments,more of the spacer material layer 415 overlaying portions of thehardmask layer 405 may remain than the spacer material layer 415overlaying the top region of the mandrels 410.

To ensure complete removal of the portions of the spacer material layer415 overlaying the mandrels 410 and to expose the mandrels 410, method300 may further include an over etch process, which may includeoperations 335-360 to be discussed below, by increasing the operationtime of the last cycle by about 5%, about 10%, about 15%, about 20%, ormore, depending on the particular applications. During over etch, theexposed portions of the hardmask layer 405, as well as the portions ofthe hardmask layer 405 underneath only very thin portions of the spacermaterial layer 415, may also be modified. If the same treatment gasprecursors as those utilized in operations 305-315 may be used for theover etch process, the modified portions of the hardmask layer 405 mayalso be removed in the subsequent removal operation, which may lead torecesses formed in the hardmask layer 405 between the sidewalls of thespacer material layer 415 and overall unevenness of the hardmask layer405. Such loss of the hardmask layer 405 may be undesirable in manyinstances. To avoid unwanted removal of the hardmask layer 405,alternative treatment gas precursors may be utilized during the overetch process.

At operation 335, a treatment gas plasma from a diluted treatment gasprecursor within the processing region may be formed. Similar to theplasma formed at operation 305, the diluted treatment gas plasma mayalso be a wafer-level, bias plasma, providing directional flow of theplasma effluents 430 of the treatment gas precursor towards theprocessed structure 400 at operation 340, as illustrated in FIG. 4E.Given the directional flow of the plasma effluents 430, at operation345, the plasma effluents 430 of the diluted treatment gas precursor mayanisotropically modify the exposed region of the processed structure400. The exposed region of the processed structure 400 that may bemodified by the plasma effluents 430 may include the remaining spacermaterial layer 415 near the top region of the mandrels 410, theremaining spacer material layer 415 near the bottom region of themandrels 410 and overlaying portions of the hardmask layer 405, andpartially exposed portions of the hardmask layer 405. Because theremaining spacer material layer 415 overlaying portions of the hardmasklayer 405 may be very thin, surface portions of the hardmask layer 405underneath the spacer material layer 415, although not exposed, may alsobe modified during operation 345. During operations 335-345, operationalconditions, such as pressure, temperature, bias plasma power, etc., maybe maintained at similar levels to those maintained during operation305-315.

The treatment gas precursors involved in operations 335-345 may be amixture of two or more gases. At least one of the treatment gasprecursors may modify the spacer material layer 415 to be removed, andat least one of the treatment gas precursors may be a dilution gas thatmay modify or passivate the hardmask layer 405 to limit subsequentremoval of the hardmask layer 405. Without intending to be bound by anyparticular theory, the dilution gas may passivate the hardmask layer 405through penetration into the hardmask layer 405, and may form a moredensely packed surface layer of the hardmask layer 405, which may not beeasily removed in the subsequent removal operation, thereby preservingthe hardmask layer 405. The treatment gas precursor that may modify thespacer material layer 415 may include nitrogen-containing and/orhydrogen-containing precursors, such as diatomic nitrogen, diatomichydrogen, and ammonia. The dilution gas may include oxygen-containingprecursors, such as diatomic oxygen, or nitrogen-containing precursors,such as diatomic nitrogen. In some embodiments, the treatment gasprecursors may include nitrogen gas diluted with oxygen gas, ammoniadiluted with nitrogen gas, or hydrogen gas diluted with oxygen gas ornitrogen gas. The dilution gas may constitute less than or about 50%,less than or about 40%, less than or about 30%, less than or about 20%,less than or about 10%, less than or about 5%, or less of the dilutedtreatment gas precursors.

To remove the modified spacer material layer 415, operations 350-360,similar to operations 320-330, may be performed. At operation 350, aremote plasma may be formed to produce plasma effluents, and the remoteplasma may be formed from a halogen-containing precursor, such as afluorine-containing precursor, similar to the remote plasma formed atoperation 320. The plasma effluents may be flowed through the processingchamber to the processing region towards the processed structure 400 atoperation 355. Upon contacting the modified spacer material layer 415,at operation 360, the plasma effluents may remove the modified spacermaterial layer 415 but may remove little of the hardmask layer 405,resulting in the processed structure 400 as shown in FIG. 4F. Althoughthe diluted treatment gas precursors are described herein in the processof over etch, the diluted treatment gas precursors may also be utilizedduring operations 305-315 because the same or even greater selectivityof the modified spacer material layer 415 by the diluted treatment gasprecursors to the unmodified spacer material layer 415 may be achievedusing the remote plasma effluents utilized in operations 320-330.

Once the portions of the spacer material layer 415 overlaying themandrels 410 may be removed and the mandrels 410 may be exposed, method300 may proceed to operation 365 to remove the mandrels 410. Themandrels 410 may be polysilicon mandrels, and may be removed using afluorine-containing precursor. For example, a remote plasma of afluorine-containing precursor, such as nitrogen trifluoride, may beformed and flowed to the processing region together with hydrogen andcarrier gases to remove the polysilicon mandrels 410, resulting in thestructure shown in FIG. 4G.

With reference to FIGS. 5, 6A and 6B, another exemplary method 500 forimproving etching selectivity of the spacer material layer 415 over thehardmask layer 405 will be described. As shown in FIG. 5, method 500 mayinclude operations 505-530 for processing a processed structure, suchthe processed structure 400 as shown in FIG. 4A. Specifically, method500 may include a modification process including operations 505-515,same as or similar to operations 305-315 of method 300, and an etchingprocess including operations 520-530, same as or similar to operations320-350 of method 300 to selectively remove modified spacer materiallayer 415 over unmodified spacer material layer 415. Operations 505-530may be performed in multiple cycles until a very thin layer of thespacer material layer 415 may remain overlaying the mandrels 410 and/orportions of the hardmask layer 405, resulting in the structure similarto that shown in FIG. 4D. Then, method 500 may proceed to an over etchprocess.

Different from method 300 where diluted treatment gas precursors may beused during the over etch process for modifying the exposed surfaces ofthe processed structure 400, method 500 may utilize treatment gasprecursors that may be the same as or similar to those used duringoperations 505-515 or operations 305-315. Accordingly, during the overetch process, method 500 may include operations 535-545 that may be thesame as or similar to operations 505-515 and/or operations 305-315.Specifically, at operation 535, a bias plasma of any treatment gasprecursor as discussed above with reference to operations 305-315 ofmethod 300 may be formed at wafer level in the processing region. Atoperation 540, the plasma effluents 610, which may be the same as orsimilar to the plasma effluents 420 described above with reference toFIG. 4B, may be directed by the plasma bias towards the processedstructure 400, as illustrated in FIG. 6A. At operation 545, the plasmaeffluents 610 may modify the exposed region of the processed structure400, such as the remaining spacer material layer 415 as well as exposedportions of the hardmask layer 405 and portions of the hardmask layer405 underlying the very thin remaining spacer material layer 415, asshown in FIG. 6A.

As mentioned above, the same etching precursors as those utilized duringoperations 520-530 or operations 320-330 may also remove modifiedportions of the hardmask layer 405. To avoid undesirable loss or removalof the hardmask layer 405 during the over etch process, method 500 mayutilize etching precursors different from those utilized duringoperations 520-530 or operations 320-330. Specifically, method 500 mayinclude, at operation 550, forming a remote plasma from ahalogen-containing precursor, such as a fluorine-containing precursor,to produce plasma effluents. At operation 555, the plasma effluents maybe flowed through the processing chamber to the processing region of theprocessing chamber where the processed structure 400 may be housed. Atoperation 560, water vapor may be flowed into the processing region andcombined with the plasma effluents. In some embodiments, the water vapormay not be passed through the remote plasma region and may be excited byinteraction with the plasma effluents.

At operation 565, the plasma effluents combined with water vapor mayselectively remove the modified spacer material layer 415 but may removelittle or none of the modified hardmask layer 405, resulting in thestructure shown in FIG. 6B. Without intending to be bound by anyparticular theory, the selective etching may be achieved due to thedifferent wetting properties water may exhibit at the modified spacermaterial layer 415 and the modified hardmask layer 405. The water vapormay be adsorbed at the modified spacer material layer 415 whereas theadsorption of water vapor at the modified hardmask layer 405 may belimited. The adsorbed water vapor at the modified spacer material layer415 may act as an catalyst for the fluorine-containing plasma effluentsto interact with and consequently remove the modified spacer materiallayer 415. Due to the lack of water catalyst at the modified hardmasklayer 405, the removal of the modified hardmask layer 405 may be limitedor substantially prevented. An etching selectivity of the modifiedspacer material layer 415 over the modified hardmask layer 405 of atleast above or about 5:1, above or about 6:1, above or about 7:1, aboveor about 8:1, above or about 9:1, above or about 10:1, or greater may beachieved. In contrast, without modifying the etching precursors utilizedduring the over etch operations 550-565, a selectivity of the modifiedspacer material layer 415 to the modified hardmask layer 405 may beabout 2:1 or less.

The plasma involved in operation 550 may be formed remotely from theprocessing region of the processing chamber. For example, the plasma maybe formed in a region of the processing chamber that is fluidly isolatedfrom the processing region of the processing chamber. Thus, the remoteplasma region may be physically separated from the processing region,while being fluidly coupled with the processing region. For example, inthe exemplary chamber of FIG. 2, the remote plasma may be generated inregion 281, which is separated from the processing region 284 by theshowerhead 225. Additionally, the remote plasma may be formed in aremote plasma unit, such as an RPS unit that is separate from thechamber, but fluidly coupled with the chamber to deliver plasmaeffluents into the chamber, such as through a lid, top plate, orshowerhead. The plasma power may be between about 50 W to 500 W. In someembodiments, the plasma power may be less than or about 500 W, less thanor about 450 W, less than or about 400 W, less than or about 350 W, lessthan or about 300 W, less than or about 250 W, less than or about 200 W,less than or about 150 W, less than or about 100 W, or less.

The fluorine-containing precursor for forming the remote plasma mayinclude one or more materials including NF₃, HF, F₂, CF₄, CHF₃, C₂F₆,C₃F₆, or additional fluorine-substituted hydrocarbons, orfluorine-containing materials. The fluorine-containing precursor may beflowed at a flow rate below or about 50 sccm, below or about 40 sccm,below or about 30 sccm, below or about 20 sccm, below or about 10 sccm,below or about 5 sccm, or lower. Given the relatively low flow rate ofthe fluorine-containing precursor, a dilution gas may be flowed togetherwith the fluorine-containing precursor to ensure uniform distribution ofthe fluorine-containing plasma effluents towards the processed structure400. The dilution gas may include helium or other inert gases that maybe flowed at a flow rate above or about 500 sccm, above or about 1,000sccm, above or about 1,500 sccm, above or about 2,000 sccm, above orabout 2,500 sccm, above or about 3,000 sccm, above or about 3,500 sccm,above or about 4,000 sccm, above or about 4,500 sccm, above or about5,000 sccm, or higher. In some embodiments, the ratio of the flow rateof the dilution gas to the flow rate of the fluorine-containingprecursor may be 50:1, 100:1, 150:1, 200:1, 250:1, or greater. In someembodiments, the flow rate of the fluorine-containing precursor may beabout 20 sccm, and the flow rate of the dilution gas, such as helium,may be about 3,500 sccm.

The delivery of water vapor may be achieved using a mass flow meter(MFM), mass flow controller (MFC), an injection valve, or by anysuitable water vapor generators. In some embodiments, the water vapormay be carried by a carrier gas, such as helium or other inert gas,flowed through a bubbler. The carrier gas may be flowed at a flow rateof above or about 400 sccm, above or about 600 sccm, above or about 800sccm, above or about 1,000 sccm, above or about 1,500 sccm, above orabout 2,000 sccm, or greater. The water vapor delivered may be above orabout 400 mgm, above or about 600 mgm, above or about 800 mgm, above orabout 1,000 mgm, above or about 1,500 mgm, above or about 2,000 mgm, orgreater. In some embodiments, 1,000 mgm water vapor may be delivered bya carrier gas of helium that may be flowed at a flow rate of 1,000 sccm.

To facilitate the adsorption of water vapor at the modified spacermaterial layer 415, the temperature at the substrate level or in theprocessing region may be maintained between about 0° C. and about 50°C., such as between about 5° C. and about 35° C. The temperature may bemaintained below or about 40° C., below or about 35° C., below or about30° C., below or about 25° C., below or about 20° C., below or about 15°C., below or about 10° C., below or about 5° C., or lower. Thetemperature may be maintained through a heat exchanger, such as the heatexchanger coil 217 embedded in the chuck 250 shown in FIG. 2. The heatexchanger coil may include one or more heat transfer fluid channelsthrough which heat transfer fluid, such as an ethylene glycol/water mix,may be passed to control the temperature of the chuck and ultimately thetemperature of the processed structure 400.

It is observed that the fluorine-containing effluents combined withwater vapor, as discussed above with reference to operations 550-565,may not only have high etching selectivity of modified spacer materiallayer 415 over the hardmask layer 405, but the fluorine-containingeffluents combined with water vapor may also have high etchingselectivity of modified spacer material layer 415 over unmodified spacermaterial layer 415. The selectivity of the modified spacer materiallayer 415 over the unmodified spacer material layer 415 may be at leastabove or about 5:1, above or about 6:1, above or about 7:1, above orabout 8:1, above or about 9:1, above or about 10:1, above or about 15:1,above or about 20:1, or greater. Accordingly, to produce the processedstructure 400 shown in FIG. 4F or FIG. 6B without removing the hardmasklayer 405, operations 505-530 of method 500 may be omitted. Rather,operations 535-560 may be performed in cycles until the mandrels 410 maybe completely exposed. As discussed above, the temperature at thesubstrate level or in the processing region during operations 550-565may be maintained within a lower range, such as between about 0° C. andabout 50° C., as compared to that maintained during operations 520-530or operations 320-330, such as between about 50° C. to about 140° C.Performing operations 535-560 only in cycles for the entire process mayeliminate the need to adjust the operating temperature for the over etchprocess.

With reference to FIGS. 7A-7C, another exemplary method for improvingetching selectivity of the spacer material layer 415 over the hardmasklayer 405 will be described. Different from method 300 where dilutedtreatment gas precursors may be used for the over etch process or method500 where different etching precursors may be used for the over etchprocess, the method as illustrated in FIGS. 7A-7C may involve selectivedeposition or coating of a protective layer over any exposed hardmasklayer 405 prior to the over etch process. Specifically, the processedstructure 400 shown in FIG. 4A may be processed using either operations305-330 of method 300 or operations 505-530 of method 500 such that avery thin layer of the spacer material layer 415 may remain overlayingthe mandrels 410 and/or portions of the hardmask layer 405, resulting inthe structure similar to that shown in FIG. 4D.

Prior to the over etch process, selective coating of a protective layerat the hardmask layer 405 may be performed by forming a bias plasma fromcarbon-containing precursors in the processing region where theprocessed structure 400 may be housed. The plasma bias may direct theflow of carbon-containing plasma effluents 710 towards the processedstructure 400, and a protective layer 720 that may be composed of carbonmay be selectively deposited at the exposed regions of the hardmasklayer 405. Due to the reaction that may happen between the carbon fromthe carbon-containing plasma effluents and the oxygen in the spacermaterial layer 415, deposition of the protective layer 730 at the spacermaterial layer 415 may be limited, resulting in the processed structure400 shown in FIG. 7A. Depending on the operating conditions, the ratioof the thickness of the protective layer 720 that may be deposited atthe exposed regions of the hardmask layer 405 to the thickness of theprotective layer 730 that may be deposited at the spacer material layer415 may be at least about 2:1, about 3:1, about 4:1, about 5:1, orgreater.

The bias plasma power may be between about 10 W to 150 W. In someembodiments, the plasma power may be below or about 150 W, below orabout 100 W, below or about 80 W, below or about 60 W, below or about 50W, below or about 40 W, below or about 30 W, below or about 20 W, orless. Because the directional deposition of the carbon-containingprotective layer may involve a form of bombardment, a relatively lowbias plasma power, such as below or about 50 W, may be utilized so as toprevent or limit surface modification of the hardmask layer 405 by theother components in the plasma effluents, thereby preventing or limitingany subsequent removal of the hardmask layer 405.

The carbon-containing precursors may include hydrocarbon precursors,such as methyl-containing precursors in embodiments. For example, thecarbon-containing precursors may include methane (CH₄). In someembodiments, the carbon-containing precursors may be flowed togetherwith carrier or dilution gases including inert gases, such as helium orother noble gases, nitrogen gas, or hydrogen-containing gases, such asammonia. The ratio of the flow rate of the dilution gases to the flowrate of the carbon-containing precursors may be about 1.5:1, about 2:1,about 2.5:1, about 3:1, about 4:1, or greater. For example, the flowrate of the carbon-containing precursors may be about 25 sccm, and theflow rate of the dilution gases, such as helium, nitrogen, or ammonia,may be about 50 sccm. In some embodiments, the carbon-containingprecursors may be flowed without any carrier or dilution gases. The flowrate of the carbon-containing precursors may be between about 5 sccm andabout 100 sccm, between about 15 sccm and about 75 sccm, or betweenabout 25 sccm and about 50 sccm in various embodiments.

A relatively low pressure of the processing region may be maintained soas to increase the directionality of the deposition of the protectionfilm. In some embodiments, the pressure may be maintained below or about200 mTorr, below or about 150 mTorr, below or about 100 mTorr, below orabout 50 mTorr, below or about 25 mTorr, below or about 20 mTorr, belowor about 15 mTorr, below or about 10 mTorr, below or about 5 mTorr, orlower. The temperature of the processed structure 400 or the processingregion may be maintained above or about 50° C., above or about 60° C.,above or about 70° C., above or about 80° C., above or about 90° C.,above or about 100° C., above or about 110° C., above or about 120° C.,above or about 130° C., above or about 140° C., or above or about 150°C. In some embodiments, the temperature of the processed structure 400or the processing region may be maintained between about 80° C. andabout 110° C., such as 90° C.

Depending on the particular application, the selective deposition of thecarbon protective layer may last less than or about 80 seconds, lessthan or about 70 seconds, less than or about 60 seconds, less than orabout 50 seconds, less than or about 40 seconds, less than or about 30seconds, less than or about 20 seconds, less than or about 10 seconds,less than or about 5 seconds, or less in embodiments. In someembodiments, the thickness of the carbon protective layer 720 depositedover any exposed regions of the hardmask layer 405 may be less than orabout 5 nm, less than or about 4 nm, less than or about 3 nm, less thanor about 2 nm, less than or about 1 nm, or less, which may providesufficient protection to limit or prevent removal of the hardmask layer405.

By utilizing the protective coating to limit or prevent undesirableremoval of the hardmask layer 405, the same treatment gas precursors orthe same etching precursors may be utilized throughout the entire methodwhen processing the processed structure 400 shown in FIG. 4A into theprocessed structure 400 shown in FIG. 4F or FIG. 6B. For example, thetreatment gas precursors involved in operations 305-315 or operations505-515 may be utilized during the over etch process. Due to therelatively thick carbon protective film 720 being deposited, thetreatment gas precursors may not modify any hardmask layer 405, whereasthe treatment gas precursors may still modify the spacer material layer415 to form a modified layer 740 of the spacer material layer 415, asshown in FIG. 7B, because the spacer material layer 415 may be coveredonly by the very thin or substantially none carbon deposition 730.Accordingly, during subsequent etching process, such as operations320-330 or operations 520-530, the modified layer 740 of the spacermaterial layer 415 may be removed, whereas no or little removal of thehardmask layer 405 may occur. With a subsequent carbon removaloperation, the processed structure 400 shown in FIG. 7C may be obtained.In some embodiments, if desired, the diluted treatment gas precursorsinvolved in operations 335-345 of method 300 and the etching precursorsinvolved in operations 550-565 of method 500 for the over etch processmay be utilized in conjunction with the protective coating or depositionto further protect the hardmask layer 405 from being removed.

With reference to FIGS. 8 and 9A-9C, another exemplary method 800 forimproving etching selectivity of the spacer material layer 415 over thehardmask layer 405 will be described. Method 800 may be utilized toperform the over etch process. Prior to operations of method 800, theprocessed structure 400 as shown in FIG. 4D may be obtained utilizingoperations 305-330 of method 300 or operations 505-530 of method 500.Method 800 may then be initiated by forming a bias plasma from a halogenand carbon-containing precursor, such as a fluorine andcarbon-containing precursor, at operation 805 in the processing regionof the processing chamber where the processed structure 400 may behoused. At operation 810, the plasma effluents 910 of the fluorine andcarbon-containing precursor may be directed by the plasma bias towardsthe processed structure 400, as illustrated in FIG. 9A. At operation815, the plasma effluents 910 may selectively remove the remainingspacer material layer 415 overlaying the mandrels 410 and portions ofthe hardmask layer 405 relative to the exposed portions of the hardmasklayer 405.

Without intending to be bound by any particular theory, the plasmaeffluents 910 produced from the fluorine and carbon-containingprecursors may react with the spacer material layer 415, which mayinclude silicon oxide, to form volatile byproducts, such as carbon oxideand silicon tetrafluoride. Due to the lack of oxygen in the hardmasklayer 405, which may include silicon nitride or titanium nitride,instead of forming carbon oxide, a layer of carbon 920 may be depositedat the exposed portions of the hardmask layer 405. Accordingly, theprocessed structure 400 shown in FIG. 9B may be obtained through method800 with the spacer material layer 415 selectively removed by thefluorine and carbon-containing precursor and the hardmask layer 405protected by the carbon deposition 920 with substantial no or littleremoval. Following a subsequent carbon removal operation, the processedstructure 400 shown in FIG. 9C may be obtained. Depending on theoperating conditions, an etching selectivity of the spacer materiallayer 415 over the hardmask layer 405 by the fluorine andcarbon-containing precursor of at least above or about 5:1, above orabout 6:1, above or about 7:1, above or about 8:1, above or about 9:1,above or about 10:1, or greater may be achieved.

The bias plasma power forming the fluorine and carbon-containing plasmaeffluents may be between about 5 W and about 100 W. In some embodiments,the plasma power may be below or about 100 W, below or about 80 W, belowor about 60 W, below or about 50 W, below or about 40 W, below or about30 W, below or about 20 W, below or about 10 W, below or about 5 W, orlower. Relatively low bias power, such as below or about 20 W, may beutilized in method 800 to achieve sufficient dissociation of thefluorine and carbon-containing precursor while limiting undesiredmodification or removal of the hardmask layer 405 due to bombardment.

The fluorine and carbon-containing precursor may include fluorocarbonprecursors. In some embodiments, the fluorine and carbon-containingprecursor may include octafluorocyclobutane (C₄F₈). The fluorine andcarbon-containing precursor may be flowed at a flow rate below or about20 sccm, below or about 15 sccm, below or about 10 sccm, below or about5 sccm, or lower. Given relatively low flow rates of thefluorine-containing precursor, a dilution gas may be flowed togetherwith the fluorine and carbon-containing precursor to ensure uniformdistribution of the fluorine and carbon-containing plasma effluentstowards the processed structure 400. The dilution gas may include heliumor other inert gases that may be flowed at a flow rate above or about100 sccm, above or about 200 sccm, above or about 300 sccm, above orabout 400 sccm, above or about 500 sccm, above or about 600 sccm, aboveor about 800 sccm, above or about 1,000 sccm, or higher. In someembodiments, the ratio of the flow rate of the dilution gas to the flowrate of the fluorine and carbon-containing precursor may be 20:1, 30:1,40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 150:1, 200:1, or greater. Insome embodiments, the flow rate of the fluorine and carbon-containingprecursor may be about 5 sccm, and the flow rate of the dilution gas,such as helium, may be about 400 sccm.

A relatively low pressure of the processing region may be maintained soas to increase the directionality of the removal of the spacer materiallayer 415. In some embodiments, the pressure may be maintained below orabout 100 mTorr, below or about 50 mTorr, below or about 40 mTorr, belowor about 30 mTorr, below or about 20 mTorr, below or about 10 mTorr,below or about 5 mTorr, below or about 1 mTorr, or lower. Thetemperature of the processed structure 400 or the processing region maybe maintained at above or about 50° C., above or about 60° C., above orabout 70° C., above or about 80° C., above or about 90° C., above orabout 100° C., above or about 110° C., above or about 120° C., above orabout 130° C., above or about 140° C., or above or about 150° C., orhigher. In some embodiments, the temperature of the processed structure400 or the processing region may be maintained at between about 80° C.and about 110° C., such as 100° C. Depending on the particularapplication, the selective etching of the spacer material layer 415 maylast less than or about 60 seconds, less than or about 50 seconds, lessthan or about 45 seconds, less than or about 40 seconds, less than orabout 35 seconds, less than or about 30 seconds, less than or about 25seconds, less than or about 20 seconds, less than or about 15 seconds,less than or about 10 seconds, less than or about 5 seconds, or less inembodiments.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theembodiments. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent technology. Accordingly, the above description should not betaken as limiting the scope of the technology.

Where a range of values is provided, it is understood that eachintervening value, to the smallest fraction of the unit of the lowerlimit, unless the context clearly dictates otherwise, between the upperand lower limits of that range is also specifically disclosed. Anynarrower range between any stated values or unstated intervening valuesin a stated range and any other stated or intervening value in thatstated range is encompassed. The upper and lower limits of those smallerranges may independently be included or excluded in the range, and eachrange where either, neither, or both limits are included in the smallerranges is also encompassed within the technology, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a layer” includes aplurality of such layers, and reference to “the precursor” includesreference to one or more precursors and equivalents thereof known tothose skilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”,“include(s)”, and “including”, when used in this specification and inthe following claims, are intended to specify the presence of statedfeatures, integers, components, or operations, but they do not precludethe presence or addition of one or more other features, integers,components, operations, acts, or groups.

1. An etching method comprising: forming a treatment gas plasma from atreatment gas precursor within a processing region of a semiconductorprocessing chamber; directing effluents of the treatment gas plasmatowards a semiconductor substrate within the processing region of thesemiconductor processing chamber; anisotropically modifying a surface ofa first material on the semiconductor substrate with the effluents ofthe treatment gas plasma; passivating a surface of a second material onthe semiconductor substrate with the effluents of the treatment gasplasma, wherein passivating the surface of the second material comprisesincreasing a density of a surface layer of the second material; forminga remote plasma from a fluorine-containing precursor to producefluorine-containing plasma effluents; flowing the fluorine-containingplasma effluents to the processing region of the semiconductorprocessing chamber; and selectively removing the modified surface of thefirst material from the semiconductor substrate.
 2. The etching methodof claim 1, at least some of the effluents of the treatment gas plasmapenetrates into the second material to increase the density of thesurface layer of the second material.
 3. The etching method of claim 1,wherein the treatment gas precursor comprises a mixture of a firstprecursor and a second precursor, and wherein anisotropically modifyingthe surface of the first material comprises anisotropically modifyingthe surface of the first material with plasma effluents of the firstprecursor.
 4. The etching method of claim 3, wherein the first precursorcomprises at least one of a nitrogen-containing precursor or ahydrogen-containing precursor.
 5. The etching method of claim 3, whereinpassivating the surface of the second material comprises passivating thesurface of the second material with plasma effluents of the secondprecursor.
 6. The etching method of claim 3, wherein the secondprecursor comprises at least one of an oxygen-containing precursor or anitrogen-containing precursor.
 7. The etching method of claim 3, whereinthe mixture comprises less than or about 20% of the second precursor. 8.The etching method of claim 1, wherein the first material comprises aspacer material including an oxide material.
 9. The etching method ofclaim 1, wherein the second material comprises a hardmask materialincluding a nitride material.
 10. The etching method of claim 1, whereinselectively removing the modified surface of the first material removessubstantially none of the modified surface of the second material fromthe semiconductor substrate.
 11. An etching method comprising: forming abias plasma from a carbon-containing precursor within a processingregion of a semiconductor processing chamber to producecarbon-containing plasma effluents; selectively depositing acarbon-containing protective layer at a surface of a first material on asemiconductor substrate within the processing region of thesemiconductor processing chamber with the carbon-containing plasmaeffluents; and selectively removing a surface of a second material onthe semiconductor substrate.
 12. The etching method of claim 11, whereinthe carbon-containing precursor comprises methane.
 13. The etchingmethod of claim 12, wherein the carbon-containing precursor furthercomprises a dilution gas, and wherein a ratio of a flow rate of thedilution gas to a flow rate of methane is about 2:1.
 14. The etchingmethod of claim 11, further comprising depositing a carbon-containingprotective layer at a surface of the second material.
 15. The etchingmethod of claim 14, wherein a ratio of a thickness of thecarbon-containing protective layer deposited at the surface of the firstmaterial to a thickness of the carbon-containing protective layerdeposited at the surface of the second material is at least about 3:1.16. The etching method of claim 14, further comprising: forming atreatment gas plasma from a treatment gas precursor within theprocessing region of the semiconductor processing chamber;anisotropically modifying the surface of the second material witheffluents of the treatment gas plasma; forming a remote plasma from afluorine-containing precursor to produce fluorine-containing plasmaeffluents; flowing the fluorine-containing plasma effluents to theprocessing region of the semiconductor processing chamber; andselectively removing the modified surface of the first material from thesemiconductor substrate with the fluorine-containing plasma effluents.17. The etching method of claim 11, wherein the carbon-containingprecursor comprises a fluorine and carbon-containing precursor.
 18. Theetching method of claim 17, wherein the carbon-containing precursorfurther comprises a dilution gas, and wherein a ratio of a flow rate ofthe dilution gas to a flow rate of the fluorine and carbon-containingprecursor is between about 20:1 and about 200:1.
 19. The etching methodof claim 11, wherein the carbon-containing protective layer comprises alayer of carbon.
 20. The etching method of claim 11, wherein the firstmaterial comprises a spacer material including an oxide material, andwherein the second material comprises a hardmask material including anitride material.